The present invention relates to heat exchangers and more particularly to heat exchangers utilised in gas turbine engines.
Heat exchange is important in order to ensure machinery and engines such as gas turbine engines remain within acceptable operational parameters for the materials from which that machinery or engine is formed as well as to achieve efficient thermodynamic operation. Generally heat exchange is performed between two fluid streams. Fluids may be liquids or gasses or combinations of the two, and phase change may also occur within a heat exchanger. The most efficient heat exchangers ensure that there is good heat transfer and low pressure loss in the fluids by optimising flow rates, and the available surface areas for heat exchange.
There are a number of prior basic types of heat exchanger including for example plate and fin type heat exchangers as shown in U.S. Pat. No. 3,866,674, cross-corrugated plate heat exchangers as shown in U.S. Pat. No. 4,014,385, tubular heat exchangers as shown in U.S. Pat. No. 5,318,180 and a refined tubular heat exchanger as described in Japanese Patent JP 2000329485. Each of these heat exchanger designs has limitations with regard to thermal performance or acceptability for different operational environments in terms of pressure capability both absolutely and in terms of pressure loss in the coolant flows themselves as well as such matters as ease of fabrication with suitable materials. Generally compromises must be made with regard to heat exchanger effectiveness in view of the above considerations as well as weight and design performance objectives.